The traditional generator has the following defects: first, when the rotor (the poles) and the stator (the coil) of traditional generators are in relative circular motion, the magnetic force lines and the coil are in relative cutting motion, the main magnetic flux and the rotational magnetic field generated by the induced current of the coil form a tangential force which is in the opposite direction of the rotor rotation direction, thus having resistance effect on the rotator.
The input power is much larger than the electromagnetic resistance to meet the operation requirement of generator. The higher the electromagnetic resistance is, the more energy is consumed. This generation mode only completes part of the energy conversion, the conversion efficiency is low, and the energy consumption is high. Second, magnetisms leakage and harmonic waves can occur to the iron core of traditional generators, which is harmful to the grid.
In addition, reducing the space between the iron core and the poles is a must to increase the generation efficiency of generators in that the smaller the space is, the smaller magnetic resistance generated by the air in the space is, and the higher the generation efficiency is. The optimized scheme is that the iron core is in direct contact with the poles so as to ensure most magnetic force lines of the poles to pass through the iron core.
However, on the one hand, the requirements on processing techniques is high and the production cost of generators is significantly increased for reducing the space between the iron core and the pole; on the other hand, since the existing iron core and the pole are solid, the generation efficiency of generators is difficult to be optimized if the frictional force from direct contact is too large.